Writing instrument



FIG. 1 is a rear view of a writing instrument of my new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a top right perspective view thereof. 

The ornamental design for a writing instrument, as shown and described. 